Cyclic thionosulfites and their preparation



United States Patent 3,3573% CYCLIC THIONOSULFITES AND THEIR PREPARATIONQuentin E. Thompson, Belleville, Ill., assignor to Monsanto Company, St.Louis, Mo., a corporation of Delaware No Drawing. Filed Dec. 28, 1964,Ser. No. 421,672

8 Claims. (Cl. 260-327) This invention relates to a new class ofcompounds and to their method of preparation. More particularly, thisinvention relates to cyclic sulfur esters of dihydric alcohols and toacyclic polymeric compounds thereof.

The novel cyclic esters of this invention can -be represented by thestructure (II) R R R where y is an integer from 0 to 10 and R and R' areeach selected from the group consisting of hydrogen, alkyl radicals,radicals having from 1 to 16 carbon atoms, cycloalkyl radicals havingfrom 5 to 6 carbon atoms; cycloalkylalkyl radicals having from 7 to 17carbon atoms, alkenyl radicals having from-2 to 16 carbon atoms,provided that the total of the number of carbon atoms of R and R is notgreater than 20, and aryl radicals and n is an integer from ()to 16.

The cyclic compounds and polymers of this invention are prepared byreacting aliphatic diols with sulfur monochloride in the presence of atleast 2 mols of tertiary amine per mol of sulfur monochloride and in thepresence of an inert diluent.

Depending upon the concentration of sulfur monochloride and diol in thereaction mixture, either cyclic monomers, acyclic polymers or mixturesthereof can be prepared according to the method of this invention. Thepresence of excess diol in the reaction mixture favors the formation ofpolymeric esters (structure II). The formation of cyclic monomericesters (structure I) is favored when substantially equimolar amounts ofsulfur monochloride and diol are brought together in an inert diluentunder dilute conditions, for example, where the molar concentration ofeach reactant in the reaction mixture is substantially equal and lessthan about .002 molar. When the diol concentration in the reactionmixture exceeds .002 molar and when the diol concentration issubstantially greater than that of the monochloride, proportionatelyless monomer and more polymer is formed. When the diol concentration inthe reaction mixture is greater than 1 molar substantially all of theproduct is a polymer (structure II).

In carrying out the process of this invention to produce polymers ofstructure II, sulfur monochloride and dihydric alcohol are each firstdiluted with an inert diluent after which the tertiary amine is combinedwith the dihydric alcohol-diluent mixture. The mixture of sulfurmonochloride and diluent is then added to the mixture of dihydricalcohol, amine and diluent. To produce compounds of structure Isimultaneous addition of sulfur monochloride and a mixture of diol andtertiary amine to a reaction zone containing an inert diluent is made soso that the molar ratios of sulfur monochloride, diol and tertiary amineare about 1:1:2, respectively, in the reaction zone and the diol andchloride concentrations are no greater than about .002 molar. Using thelatter procedure but allowing reactant concentrations above about .002molar produces a mixture of esters of structures I and II. The esterscan be easily separated from each other by con ventional means such asby fractional distillation. The reaction of the diol with sulfurmonochloride takes place at temperatures in the range of about 50 C. toabout C. and preferably from 0 C. to 25 C. Although the reaction takesplace nearly instantaneously, it is usually advisable to agitate thereaction mixture during the addition of sulfur monochloride and for ashort time thereafter to assure completion of the reaction and propercontrol of reaction temperature.

The tertiary amine used in the process of this invention functions as anacid acceptor in the reaction mixture and forms a hydrochloride salt bycombining with hydrogen chloride which is formed as a byproduct in thereactior of alcohol and sulfur monochloride. At the completion of thereaction, removal of the amine salt is conveniently accomplished byextraction with water, preferably ice H a water. The water soluble aminesalt separates from the Water-insoluble sulfur esters and is decantedwith the aqueous phase of the mixture.

An inert or neutral diluent is employed inproducing cyclic esters tocontrol the concentration of the reactants and to render thereaction'mixture stirrable during and after completion of the reaction.In the case of cyclic esters the amount of diluent needed is dependenton the amount of sulfur monochloride and diol employed. Au inert diluentis employed in producing polymeric esters to render the reaction mixturestirrable during and after completion of the reaction. In the case of.producing polymers-the amount of diluent will vary depending upon thecharacteristics of the particular diol employed and the solubility ofthe amine hydrochloride produced. One skilled in the art can easilydetermine the amount of diluent convenient for particular compounds byfollowing the teaching of the examples hereinafter set forth. Inpreparing either cyclic or polymeric esters of this invention, thediluent is selected so that its volatility will be suflicientlydifferent from that of the desired ester to ensure easy separation ofthe two materials. The crude ester, depending on its physicalproperties, is purified by conventional techniques such as distillation,crystallization or solvent extraction.

Typical examples of diluents useful in the method of this invention arechlorinated hydrocarbons, such as carbon tetrachloride, trichloromethane(chloroform) and preferably dichloromethane (methylene chloride) andaliphatic and cycloaliphatic ethers such as diethyl ether,tetrahydrofuran, diisopropyl ether and dioxane. Also, tertiary amine canbe used as a diluent by adding an amount in excess of that required tocombine with all of the hydrogen chloride produced by the reaction.

Dihydric alcohols which can be employed in the method of this inventionto produce cyclic esters include aliphatic 1,2- and 1,3-diols havingfrom 2 to 18 carbon atoms, cycloalkyl aliphatic 1,2- and 1,3-diolshaving from 8 to 20 carbon atoms and olefinic 1,2- and 1,3-diols havingfrom 4 to 24 carbon atoms. Dihydric alcohols which can be employed inthe method of this invention to produce polymeric esters include anyaliphatic diol, substituted aliphatic diol and cycloalkyl diol havingfrom 2 to 18 carbon atoms, regardless of the relative position of thehydroxyl groups.

As used herein, the term 1,2- and 1,3-diols is intended to meanaliphatic alcohols, substituted aliphatic alcohols and cycloaliphaticalcohols containing two hydroxyl groups, each group attached to adjacentcarbon atoms (1,2-) or to carbon atoms separated by not more than onecarbon atom (1,3-) of the aliphatic compound.

Tertiary amines suitable for use in the method of this invention arethose capable of forming amine salts with hydrogen chloride. Aliphatic,heterocyclic and aromatic amines are capable of utilization. Typicalamines are trialkyl amines wherein the alkyl radicals have from 1 to 12carbon atoms, examples of which are trimethylamine, tripropylamine,tributylamine, tri-n-decylamine, dimethylethylamine, dipropylbutylamineand dimethylcyclohexylamine; heterocyclic amines, examples of which arepyridine, quinoline, pyrimidine, N-methylpiperidine and N-ethylmorpholine and aromatic amines, examples of which areN,N'-diethylaniline, N,N-dimethylaniline and N-rnethyl diphenylamine. Asa practical matter a small amount in excess of the stoichiometric amountrequired can be employed to assure that all of the hydrogen chlorideformed goes to the hydrochloride salt and thereby prevent any reactionof the ester with hydrogen chloride.

The acyclic polymers of this invention prepared from 1,2- and1,3-aliphatic diols can be catalytically degraded to form the cyclicmonomer. The polymers degrade readily upon heating to a temperature inthe range of about 50 C. to about 130 C. in the presence of catalyticamounts of alkali metal al-koxide, i.e., 0.1 to mol percent of alkoxidebased on the aliphatic diol content of the polymer. The cyclic monomerproduced by polymer degradation can be removed from the reaction vesselupon formation as by distillation under reduced pressure.

Typical examples of alkali metal (Na, Li, K) alkoxides useful ascatalysts in preparing the cyclic monomer compounds of this invenitonfrom their polymeric form are sodium methylate, lithium ethylate,potassium methylate, sodium ethylate, sodium butylate, potassiumethylate, 2,3-disodium di butylate, 1,2-disodium diethylate,I,2-dipotassium dibutylate, 3,4-disodium dioctylate, 1,2-disodiumdinonylate, 1,2-dipotassium dioctylate and 1,2-dipotassium dibutylate.

The following examples illustrate specific embodiments of this inventionbut are not to be construed as limiting its scope. Compositions aregiven as percent by weight. Parts are parts by weight. The reactoremployed in all of the following examples was equipped with means fordetermining temperature of the reactants, means for agitating thecontents and means for the addition and removal of the reactants andproducts.

I. PREPARATION OF 'CYCLIC MONOMERS Example 1 Into a first containerthere was added 45 parts of 2,3- butanediol, 2 parts of triethylamineand 500 ml. of dry methylene chloride. Into a second container was added675 parts of sulfur monochloride and 500 ml. of methylene chloride. Oneliter of alcohol-free trichloromethane was placed in a suitable reactionvessel. After cooling the trichloromethane in the reaction vessel to atemperature between 5 C. and 10 C., slow concurrent addition ofreactants from the first and second containers was begun so that theamount of sulfur monochloride in the reaction vessel at no time exceededthat of 2,3-butanediol. The addition was accomplished over a period offive hour ile maintaining rapid agitation and the above- Example 2Generally following the procedure of the previous example, parts ofethylene glycol, 204 parts of triethylamine and 1 literof dry methylenechloride were combined with parts of sulfur monochloride in admixturewith 1 liter of dry methylene chloride in a reaction vessel containing1.5 liters of trichloromethhane previously cooled to a temperaturebetween 5 C. and 10 C. After completion of the reaction the product,cyclic ethylene thionosulfite, was recovered as a colorless fluid havingan index of refraction, n of 1.5638.

Example 3 Following the procedure of Example 1, 90 parts of 1,3-butanediol, 204 parts of triethylamine and 1 liter of dry methylenechloride were combined with 135 parts of sulfur monochloride inadmixture with 1 liter of dry methylene chloride in a reaction vesselcontaining 1.5 liter of trichloromethane previously cooled to atemperature between 5 C. and 10 C. After completion of the reaction, thereaction mixture was vacuum distilled yielding a yellow oily liquid. Thedistillate was purified by repeated fractional distillations. Theresulting product was identified as pure cyclic 6-methylpropylenethionosulfite having a boiling point of 40 C. (1 mm. Hg) and an index ofrefraction, n of 1.5291. The pure material was subjected to elementalanalysis, the results of which appear in the table below.

II. PREPARATION OF POLYMERS Example 4 Into a suitable reaction vesselthere was charged 90.1 parts of 2,3-butanediol, 204 parts oftriethylamine and 500 ml. of methylene chloride. The mixture was cooledto 10 C. and 135 parts of sulfur monochloride in admixture with ml. ofmethylene chloride was added over a period of2 hours with agitation at10 C. to 15 C. The reaction mixture was agitated for 15 minutes aftercompletion of the addition and wasthen washed with water to remove theamine hydrochloride. The diluent was removed from the residue byevaporation under reduced pressure leaving 147 parts of a viscous redoil having an average molecular weight of 845. The'oi'l was subjected toelemental analysis, the results of which appear below.

l Carbon, Hydrogen, Sulfur,

l percent percent percent;

Calculated for (OQHaOQSQX-HH 31. 56 5. 30 42. 13 Found 31. 38 5. 43 40.80

Using the procedure of Example 4, other esters were produced, andcharacterized. These compounds are listed in Table I below.

TABLE I Reactants Percent S Example Average N o. Product Molecular yD101 Parts 01 Amine Parts Diluent Ml. Calculated Found Weight er sPropylene 76. 1 135 Triethyl- 204 Methylene 650 (C H6O S y 46. 40 45. 611, 100 8 glyc amine. chloride. Etlliylezlie 62.0 135 do 204 o 650 1140595; 51.64 50.50 780 6 g yco 1, 4-butane-diol 90.1 135 do .do 650 (Cir180 8 42.13 42.2 960 6 1, 3-butane-diol 90.1 135 do d 650 (C4H802S2)y42.13 41.63 1,175 8 Philsnyllethylene 138.2 135 -do 650 (082180 8 31.9731.20 1,040

g Y 1,10-decanedio1.. 174.0 135 do do 650 (C10H2002S2)y 27.10 27.00 8303 III. POLYMER DEGRADATION Example 11 Into a reactor equipped with aheavy paddle stirrer, temperature sensingmeans, distillation head andmeans for addition and removal of reactants and products, therewas'charged 145 parts of the product of Example 3, and 10 ml.'of 2,3-butanediol in which 0.5 gram of metallic sodium had been dissolved.The mixture was cautiously Carbon, Hydrogen, Sulfur,

percent percent percent Calculated for 04118028; 31. 56 6. 30 42.13Found 31. 50 5.55 41.88

In addition to the dihydric alcohols employed in the foregoing examples,other dihydric alcohols can be used to prepare cyclic compounds andpolymers of this invention, for example, 1,2-pentanediol,1,3-pentanediol, 2,3- pentan'ediol, 1,5-pentanediol, 3,4-octanediol,1,2-octanediol,.1,8-octanediol, 1,2-decanediol, 1,3-decanediol, 3,4-decanediol, 1,9-nonanediol, 1,3-nonanediol, 1,2-nonanediol, l,6-hexanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2- octadecanediol,1,5-octadecanediol, 1,2-tridecanediol, 1,5- tridecanediol,4-cyclohexyl-l,3-butanediol, 4-cyclohexyl- 1,2-butanediol,3-cyclohexyl-1,2-ethanediol, 3- yclopentyl- 1,2-ethanediol,4-cyclopentyl-1,Z-butanediol and 4-cyclo pentyl-1,3-butanediol.

The novel cyclic compounds of this invention are useful as additives toincrease the lubricity of mineral oils as demonstrated by the data inTable II, below. The data were obtained on a Shell Four-Ball ExtremePressure Testing machine using steel-on-steel balls, a rotational speedof 1730 r.p.m., a temperature of 25 C. and kilogram loads as indicated.The duration of the test was one minute at each load on fresh balls. Thecontrol lubricant employed was SAE grade 90 mineral oil. The compoundsof the invention were added to the mineral oil in an amount sufiicientto provide a final composition containing 0.80% sulfur by weight.

TABLE II Scar Diameter, mm.

Many of the novel esters of this invention are useful as curing agentsfor the vulcanization of sulfur vulcanizable rubber. This property ofthe instant compounds is illustrated by the data in the following table.

Rubber stocks were compounded in parts by weight as Six rubber stocksamples were prepared using the above-stated formulations but withdifierent curing agents which are listed below. Stock No. 1 was preparedwith a commercial curing agent Widely used in current methods of rubbercuring and is employed here as a control providing a basis of comparingcuring activity.

Stock No. Curing Agent 4,4-dithi0dimorpholine.

Polymer product of Example 7.

Cyclic 1,2-dimethylethylene thionosulfite (Product of Example 1).

Polymer product of Example 4.

Polymer product of Example 3.

Polymer product of Example 8.

The stocks so compounded were cured by heating in a press for 30 minutesat 144 C. The physical properties of the vulcanizates illustrate thepowerful curing action of the new compounds.

TABLE III Modulus of Elasticity Tensile at Ultimate Stock in lbs/in. atBreak in Elongation,

Elongation of 300% lbs/in. percent 1 NC 1 NC 1 NC 2, 540 4, 260 500 1,730 3, 760 570 2, 350 4, 200 500 2, 440 4, 250 500 1,320 2, 870 500 1 Nocure.

The cyclic esters of this invention are capable of isomerism dependingon whether the double bonded sulfur atom is cis or trans to the otherring substituents. No distinction as to isomeric form has been madeherein and each reference to the cyclic compounds of this inventionWhether by name or structure is intended to include both isomeric formsthereof.

While this invention has been described with respect to various specificexamples and embodiments, it is understood that the invention is notlimited thereto and that it can be variously practiced within the scopeof the following claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A compound represented by the structure where R and R are eachselected from the group consisting of hydrogen, alkyl radicals havingfrom 1 to 16 carbon atoms, cycloalkyl radicals having from 5 to 6 carbonatoms, cycloalkylalkyl radicals having from 7 to 17 carbon atoms,alkenyl radicals having from 2 to 16 carbon atoms, providing that thetotal of the number of carbon atoms of R and R is not greater than 20,and n is an integer from 0 to 1.

2. Cyclic1,2-dimethylethylene thionosulfite.

3. Cyclic l-methylethylene thionosulfite.

4. Cyclic ethylene thionosulfite.

5. The method of preparing a compound of claim 1 which comprisesreacting in substantially equimolar amounts an aliphatic dihydricalcohol selected from the group consisting of 1,2-diols and 1,3-diolswith sulfur monochloride in the presence of at least two mols of atertiary amine per mol of sulfur monochloride in an inert diluentwherein the molar concentration of each of said alcohol and monochlorideis not greater than about .002 molar.

6. The method of preparing cyclic 1,2-dimethylethylene thionosulfitewhich comprises reacting in substantially equirnolar amounts2,3-butanediol with sulfur monochloride in the presence of at least twomols of a tertiary amine per mol of sulfur monochloride in an inertdiluent wherein the molar concentration of each of said diol andmonochloride is not greater than about .002 molar.

7. A process which comprises reacting an aliphatic dihydric alcohol withsulfur monochloride in the presence of at least two mols of tertiaryamine per mol of sulfur monochloride in an inert diluent wherein themolar coricentration of said alcohol is greater than about .002 molarand is greater than that of the said monochlor de.

8. The method of preparing a compound of claim 1 which comprises heatinga compound of the structure where z is an integer from 0 to 10, R and Rareeach selected from the group consisting of hydrogen, alkyl radicalsand cycloalkyl radicals having from 1 to 16 carbon atoms, alkenylradicals having from 1 to 16 carbon atoms, providing the total of thenumber of carbon atoms of R and R is not greater thanZO, and arylradicals, in the presence of a catalytic amount of an alkalimetalralkoxide.

References Cited UNITED STATES PATENTS 2,448,767 9/1948 Carlson 260284OTHER REFERENCES Thompson et al.: J. Org. Chem, 30 (8), pages 2696- 2703(1965).

JAMES A. PATTEN, Primary Examiner;

1. A COMPOUND REPRESENTED BY THE STRUCTURE